Freescale Optimizes LDMOS Radio Frequency Integrated Circuits for WiMAX

Freescale Semiconductor introduced three high power LDMOS Radio Frequency Integrated Circuits (RFICs) that allow designers of RF power amplifiers for WiMAX base stations to reduce costs, form factors and part counts. The devices are engineered to also increase performance and reliability when compared with amplifiers employing discrete RF power transistors.

The devices extend Freescale’s portfolio of RFICs to the two primary bands utilized by WiMAX throughout the world – 2.7 GHz and 3.5 GHz. They are the first RFICs available in over-molded plastic packages to operate at these frequencies, enabling them to leverage cost and mechanical stability advantages. They are also the first such devices to integrate multiple gain stages into a single over-molded plastic packaged device, thereby reducing cost, size and complexity.

The MW7IC2725N and MW7IC2750N RFICs operate from 2.3 to 2.7 GHz, and the MW7IC3825N operates from 3.4 to 3.6 GHz. All three devices use Freescale’s seventh-generation high-voltage (HV7) LDMOS process technology, which has been deployed worldwide in discrete field-effect transistors (FETs), as well as in RFICs for wireless applications operating at 900 MHz and 2 GHz.

RFICs Deliver Multiple Benefits
RF power amplifiers employed in WiMAX base stations typically require three or four stages of amplification delivered by discrete RF power transistors to achieve the desired output power. The use of RFICs has significant advantages over this traditional approach. By integrating two stages of gain in a single package, RFICs reduce the number of required individual devices. In most cases, the higher RF output power of the RFICs allows for the elimination of the predriver stage in WiMAX. The devices also can be used along with discrete LDMOS FETs to produce even higher RF output power.

The RFICs can further reduce cost because the capacitors, inductors and resistors required on the circuit board are integrated within the device to provide the same inter-stage impedance matching networks. This minimizes board space and reduces design complexity. System cost savings are further compounded when combined with the inherent cost savings of approximately 25 percent, provided by over-molded plastic packaging versus current air-cavity packages.

“WiMAX is a very promising technology, but it faces strong competition from existing wireless services, making it essential that WiMAX infrastructure equipment be as cost-effective as possible,” said Gavin P. Woods, vice president and general manager of Freescale’s RF Division. “These RFICs can play a key role in this critical cost reduction. Our parts not only help reduce amplifier cost, size and complexity by integrating multiple gain stages in a single device, but they also offer the inherent cost savings of over-molded plastic packaging.”

Key Specifications for Freescale’s RFICs

  • MW7IC2725N: 25 W CW output power at 1 dB gain compression point (P1dB) and at 4 W average power; 28 dB gain, 17% efficiency, Adjacent Channel Power Ratio (ACPR) at 5.25-MHz offset of -50 dBc in 500 kHz channel bandwidth
  • MW7IC2750N: 50 W CW output power at 1 dB gain compression point (P1dB) and at 8 W average power; 26 dB gain, 17% efficiency, ACPR at 5.25-MHz offset of -49 dBc in 500 kHz channel bandwidth
  • MW7IC3825N: 25 W CW output power at 1 dB gain compression point (P1dB) and at 5 W average RF output power; 23.5 dB gain, 15% efficiency, ACPR at 5.25-MHz offset of -49 dBc in 500 kHz channel bandwidth

These devices operate from a 28 to 32 VDC supply and are extremely rugged, with the ability to handle a VSWR of 10:1 at 32 VDC while delivering their rated CW output power.

With the use of Freescale’s innovative over-molded plastic packaging, the RFICs are designed to also achieve tight mechanical tolerances, enabling designers to maintain the high manufacturing yields required at WiMAX frequencies, which have been difficult to accomplish when using traditional discrete devices.

The RFICs incorporate electrostatic-discharge (ESD) protection, making them less susceptible to damage during the manufacturing process. This ESD protection enables a greater negative gate-source voltage swing, which improves device performance when operating in Class C mode.

The MW7IC2725N, MW7IC2750N and MW7IC3825N devices are sampling now and full production is expected in Q1 2008. For specific sampling and pricing information, please contact Freescale Semiconductor, a local Freescale sales office or an authorized distributor.

About Freescale Semiconductor
Freescale Semiconductor is a global leader in the design and manufacture of embedded semiconductors for the automotive, consumer, industrial, networking and wireless markets. The privately held company is based in Austin, Texas, and has design, research and development, manufacturing, or sales operations in more than 30 countries. Freescale is one of the world’s largest semiconductor companies, with 2006 sales of $6.4 billion (USD).

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